Process for the manufacture of zinc-oxide catalysts



P rental-eh. 17, 1931 UNITED STATES PATENT OFFICE WALTER BADEB AN D STANLEY JOSEPH GREEN, 0] SPONDON, NEAR DERBY, ENGLAND,

ASSIGNORB TO CELANESE CORPORATION OF AMERICA, A CORPORATION OF DELA- WARE PROCESS FOR THE MANUFACTURE O1? ZINC-OXIDE CATALYSTS This invention relates to the manufacture of methyl alcohol and to catalysts for use therein.

It is known that methyl alcohol can be prepared from gas mixtures containing hy roen and an oxide or oxides of carbon by leadmg them over catalysts, under pressure and at a temperature between about 250 and 450 C. A very large number of substances have been proposed as catalysts for this react1 on, but it is generally known that only zinc oxide, ormixtures containing zinc oxide are economically successful.

As a rule zinc oxide forms the bulk of the catalyzing mixture, its action being enhanced vby relatively small amounts of so-called romoters. For this purpose, oxides of c romium are nerally favoured, and also small amounts 0 copper.

It has now been found that the physical condition of the zinc oxide, which depends .upon the method of its preparation, is much a more important .for its activity than the presence of promoters. A zinc oxide, which by itself is only moderately active, certainly becomes activated by the addition of 5-.10% of chromic acid, but the effect of the same promoter upon a zinc oxide which is already cohol, an

i hly active, is quite small.

ure' zinc oxide can be relatively inactive as a catal st for the formationvof methyl al- 3 it ma show every possible degree activity, wit out any apparent chemical reason. a a

The present invention makes possible the preparation ofa highly active pure oxide are thereby minimized.

catalyst which does not require the presence of any promoter, its activity being in fact hardly influenced by a promoter. The use of a chemically pure substance as a catalyst has the advantage that undesirable by-reactions According to the present invention, a highly active form of zinc oxide is prepared by heating a zinc carbonate gel to a temperature not higher than that used in the catalytic preparation of methyl alcohol, and the zinc oxide so prepared is used as catalyst in the synthetic production of methyl alcohol '80 Drawing. Application filed September 15, 1927, Serial No. 219,804, and in Great Britain May 2, 1927.

from mixtures containing hydrogen and OX- ides of carbon.

The temperatures used for converting the zinc carbonate gel into zinc oxide lie between about 250 C. and 450 (3., and preferably between about 250 C. and 350 or 400 C.

The type of zinc carbonate gel employed is of considerableimportance. The more colloidal and gelatinous it is, the greater is the catalytic activity of the zinc oxide finally obtained. Zinc carbonate gels of this kind can be obtained by precipitation in very dilute solutions at ordinary or low temperature. They should not be brought to a denser state by filtering or pressing, but, after washing by decantation, the water should be removed by drying. The complete removal of electrolytesfrom the precipitate is important for the production or zinc oxide catalyst of high activity. In order to increase thevoluminous character of the product, the drying of the zinc carbonate gel may be effected by heating under vacuum or'reduced pressure.

t is preferred to precipitate the zinc carbonate 1n the presence of solutions or jellies containin suitably inert protective colloids, e. g. starc ,pectin, saponin, silica, etc., or to mix the precipitate, after washing, with solutions or jellies of such bodies. This not only enhances the activity of the zinc oxide 1 finally obtained, but also facilitates the formation of the dried mass into convenient granules. In this case also, the product ma be dried by heating under vacuum.

e followin example shows one of the many ways in w 'chthe invention can be carried out.

Example a strength, with good agitation. The end-- nous precipitate is'thoroughlywashe with water by decantation, thenymixed with a starch jelly and dried at about. C. The dry mass is broken into pieces of about inch size and charged into the reaction cham- -ber used inthe'synthesis of methyl alcohol. At the prevailing-temperature, e. g. 250 to 2 measso 300 (1, the zinc carbonate gel is converted body with the zinccarbonate gel during its into a light, flufi'y form or zinc oxide disformation. In somecases, it is possible to playing a high degre of activity when used form a suitable mixture by co-precipitation as catalyst in the production of methyl al- "from a solution containing a mixture of salts 5 cohol by the hydrogenation of oxides of caror compounds. For instance, azinc oxide 70 bon. containing chromium oxide as promoter can Dilute solutions of any other soluble zinc be obtained by precipitating the zinc carsalt (e. g. zinc sulphate or chloride), or of a bonate gel from a solution containing a. zinc sodium bi-carbonate or any other soluble carsalt and a chromium salt, and drying and bonato or bicarbonate (e. g. potassium or amheating the resulting gelatinous precipitate monium carbonate or bicarbonate) may be in the manner previously described. I substituted for the zinc nitrate and sodium What we claim and desire to secure bycarbonate in the production of the zinc car- Letters Patent is: I bonate gel. 1. A process for the manufacture of a zinc I The proportions and concentrations of the oxide catalyst for use in the synthesis of 80 reagents may be varied as desired always methyl alcohol from mixtures of hydrogen p'rovided that a zinc carbonate gel of -a and oxides of carbon, which comprises heatsuiiiciently voluminous character is obtained ing aizinc carbonate gel at a temperature not as the result of the reaction. exceeding the temperature at which: the

2 The zinc carbonate gel maybe mixed with catalyst is to be employed in the synthesis of 35 solutions or jellies of suitably inert pro methyl alcohol. tective colloids such starch, pec imsaponin, 2. A process according to claim 1, which or silica. or may be formed in the presence 01" comprises precipitating the zinc carbonate such solutions or jellies, or it may be pregel in very dilute solution.

pared and converted into zinc oxide catalyst 3. A process according to claim 1 which 90 in the entire absence of such colloids. comprises incorporating a solution or jelly As previously explained, it is convenient of a protective colloid with the zinc carto effect the conversion of the zinc carbonate bonate gel. gel into zinc oxide during the synthesis of the is. A process according to claim 1, which methyl alcohol. For example, the zinc carcomprises precipitating the zinc carbonate' bonate gel may be placed in a suitable reacgel in the presence of a solution or jelly of tion chamber maintained at a temperature of a protective colloid. 250 to 3&0" (l, for example 388 {1, through 5. A process according to claim 1, wherein which a mixture containing approximately the zinc carbonate gel is converted into'zinc' two arts by volume of hydrogen and one oxide catalyst at a temperature not exceedpart by volume ofcarbon monoxide is passed ing 450? C. under a pressure of about 80 to 120 atmos- 6. A process according to claim 1, wherein heres. As the conversion of the zinc carthe zinc carbonate gel is converted into zinc onate gel into zinc oxide proceeds, methyl oxide catalyst at a temperature. between 40 alcohol is produced in quantities which about 256 C. and 350 (1. 105,

rapidly increase to a maximum. '3. A process according to claim 1, wherei The conversion of zinc carbonate gel into in the zinc carbonate gel, While incorporated zinc oxide may however be eiiectcd as an with a solution or jelly of a protective col-- entirely separate operation under conditions loid, is converted into a zincv oxide catalyst similar to or (littering from those obtaining at a temperature between about 250 C. and

in the methyl alcohol synthesis. Thus, for -06 C. I instance, a zinc oxide may be produced from 8.1%. catalyst for use in the synthesis or a zinc carbonate gel atlow temperature unmethyl alcohol, comprising a zinc oxidehavder atmospheric pressure, and usedaftering a gel structure.

wards in the production of methyl alcohol *9. A zinc oxide catalyst prepared by 'heat at a higher temperature. I ing .a .zinc--carbonate gel at a temperature i The ,inc oxide Prepared in accordance between about 250 Grind 450 0. with the process forming the subject matter 16. A zinc ox decatalysti prepared byof the present intention may also be emheating a composition comprising a zinc can Tp1 y m iiifu with a promoter, or .bonate gel and a protective colloid at a. temi inixed' with other catalystssuitable for comperature between about 250 .C. and-450. C. 'bming hydrogen with oxides ofcarbon, or In testimony wl'iere0f.w e have hereunto -mixed with or distributed over an inert'solid "subscribed our names.

carrier, such as pumice or carbon. Such v 'WALTER BADER.

30 mixtures or preparations may be formed I STANLEY JOSEPH GREEN.

vafterthe conversion of the zinc carbonate I gel into 'zinc oxide, or, in "suitable cases, by i mixing the added substance with the zinc carbonate gel beforefor after the drying '65, operation, ,or by incorporatingthe adds 

